Ultrasonic gas leak detectors measure the sound pressure waves generated by the turbulent flow when gas escapes from higher pressures to the ambient atmosphere. Such gas leak detectors are used as industrial safety devices to monitor the unwanted or unexpected release of combustible or toxic gases into the atmosphere. The leaks need to be identified quickly before they grow further in magnitude, to allow for timely remedial action to be taken.
Conventional ultrasonic gas leak detectors are threshold devices that cannot discriminate between the ultrasound created by other manmade or natural sources, such as machinery, electrical discharge, acoustic speakers or biological sources, from those produced by real gas leaks. A way to mitigate false alarms, avert nuisance trips, and avoid costly unwarranted process shutdowns with such ultrasonic gas leak detectors is to raise the alarm threshold level several decibels above the background ultrasonic level. Raising the alarm level has the drawback of reducing detection distance to the gas leak, thereby the total area of coverage, or of ignoring gas leaks until they build up in severity, often with catastrophic consequences. Another precaution against false alarms is via the use of lengthy time delays which result in undesirable delays to the remedial action in case of a dangerous gas leak, negating the benefit of the fast response time inherent with ultrasonic gas leak detectors.
Another drawback of conventional ultrasonic gas leak detectors that depend on thresholds and time delays for their functionality is the inability to effectively verify their performance in the field, and to conduct functional safety checks at proof test intervals. The conventional gas leak detectors are unable to differentiate between the sound emitted by a real gas release and a remote ultrasonic test source to be used for periodic system performance check. This is a major inconvenience to the industrial facility that leads to either the bypassing of critical proof testing or a significant operating cost burden. Conventional ultrasonic gas leak detectors provide maintenance personnel with no means to test the gas leak detector without the disruption caused by disabling alarms.